Two-stage process for producing naphtha from petroleum distillates

ABSTRACT

A HYDROCARBON CONVERSION PROCESS COMPRISING HYDROCRACKING A PETROLEUM DISTILLATE IN A FIRST CONVERSION ZONE, RECOVERING AT LEAST ONE HYDROCRACKED PRODUCT, SUBJECTING A PORTION OF THE EFFLUENT FROM SAID FIRST CONVERSION ZONE BOILING GENERALLY ABOVE SAID HYDROCRACKED PRODUCT TO HYDROCRACKING AND DEHYDROGENATION IN A SECOND CONVERSION ZONE WITHOUT A NET CONSUMPTION OF HYDROGEN, AT A TEMPERATURE IN THE RANGE 825* TO 950*F. AND A PRESSURE IN THE RANGE 0 TO 1500 P.S.I.G., AND RECOVERING AT LEAST ONE UPGRADED NAPHTHA PRODUCT FROM SAID SECOND CONVERSION ZONE.

May 2, 1972 MASON 3,660,270

Y Two-STAGE PROCESS FOR PRODUCING NAPHTHA FROM PETROLEUM DISTILLATES Filed Jan. 15, 1970 AI'TORNEYS kw "M M w R A OM Q T J 2 a E; v V m wo v M Q .503 o .503 [2 m m m m m m \N 28 O O OOWD E a MD & w W 2 96 a 93 3: v m m w N W N 9 aw u u Q "I E 3203 4 4 30.6mm auuw F r 1 235032; E on u United States Patent Oflice 3,660,270 TWO-STAGE PROCESS FOR PRODUCING NAPH- THA FROM PETROLEUM DISTILLATES Harold F. Mason, Berkeley, Calif., assignor to Chevron Research Company, San Francisco, Calif. Continuation-impart of application Ser. No. 763,603, Sept. 30, 1968. This application Jan. 15, 1970, Ser.

Int. Cl. C10g 23/00, 37/04 US. Cl. 208-59 5 Claims ABSTRACT OF THE DISCLOSURE RELATED APPLICATION This application is a continuation-in-part of Harold F. Mason application Ser. No. 763,603, filed Sept. 30, 1968 (now abandoned), entitled Two-Stage Process for Producing Naphtha from Petroleum Distillates.

INTRODUCTION This invention relates to a hydrocarbon conversion process, and particularly to a process for the catalytic conversion of petroleum distillates to produce gasoline.

PRIOR ART It is known that hydrocracking processes are useful in gasoline manufacture, both alone and in combination with other processing steps. For example, in a conventional hydrocracking operation a petroleum distillate is hydrocracked to produce a light gasoline or naphtha product boiling generally in the range C 180 F., a heavy gasoline or naphtha fraction boiling generally in the range l80-400 F., and a fraction boiling above said heavy gasoline or naphtha fraction, and said heavy gasoline or naphtha fraction is upgraded by subjecting it to catalytic reforming. However, in such a conventional operation the end point of the feed to the catalytic reformer is limited, and all materials in the hydrocracking zone efiluent boiling above said heavy gasoline or naphtha fraction must be recycled to the hydrocracking zone or otherwise processed or disposed of 'without passing them to the catalytic reformer.

There has been a need for a combination process in which materials in the eflluent from a hydrocracking zone boiling appreciably higher than 400 F., and more particularly up to at least 500 F., and preferably higher, could be directly converted to gasoline boiling range products of quality comparable to that of gasoline products from a conventional catalytic reformer, without first recycling these materials to the hydrocracking zone to convert them to lighter hydrocracked products and then subjecting at least a portion of said lighter hydrocracked products to conventional catalytic reforming. It is an object of the present invention to provide such a combination process.

DRAWING The invention will be more clearly understood, and further objects and advantages thereof will be apparent,

3,660,270 Patented May 2, 1972 from the following description when read in connection with the accompanying drawing. The drawing is a diagrammatic illustration of apparatus and flow paths suitable for carrying out the process of the invention.

STATEMENT OF INVENTION 'In accordance with the present invention there is provided a process for producing gasoline which comprises hydrocracking a petroleum distillate in a first conversion zone, separating the efliuent from said first conversion zone into a light naphtha fraction having an end boiling point between about 180 and 280 F., a second fraction having an initial boiling point between 180 and 280 F. and an end boiling .point between about 500 and 600 F., and a third fraction boiling above about 500 -F., hydrocracking and dehydrogenating said second fraction in a second conversion zone in the presence of a catalyst comprisig an acidic cracking component and a hydrogenation-dehydrogenation component, at a hydrogen/ oil ratio of 3 to 15, and at a combination of temperature and pressure that results in no net hydrogen consumption, said temperature being in the range 825 to 950 F., and said pressure being from 0 to 1500 p.s.i.g., and recovering from said second conversion zone at least one naphtha product.

Further in accordance with the present invention, said third fraction may be recycled to said first conversion zone. Similarly, a fraction boiling generally above said naphtha product may be separated from the eflluent from said second conversion zone and recycled to said second conversion zone.

Hydrogen may be recycled to said first conversion zone from the effluent thereof, and to said second conversion zone from the effluent thereof.

In a preferred and unusually useful embodiment of the process of the present invention, said second conversion zone may be operated with a net production of hydrogen, at least a portion of which may be recycled to said first conversion zone to aid in supplying the requirements thereof.

HYDROCARBON FEEDSTOCKS Suitable hydrocarbon feedstocks for said first conversion zone are petroleum distillates, for example straightrun gas oils and cracked gas oils, boiling in the range of from about 300 to 1050 F., and preferably from 400 to 850 F.

NITROGEN CONTENT OF FEEDSTOCKS While the invention can be practiced with utility with hydrocarbon feeds to the hydrocracking zone which contain relatively large quantities of organic nitrogen, particularly when the hydrocracking catalyst comprises a crystalline zeolitic molecular sieve component, the operation becomes much more economical with stocks containing less than 200 parts per million (p.p.m.) organic nitrogen, preferably less than p.p.m., and more preferably less than 10 p.p.m. A reduction in the organic nitrogen content of a hydrocarbon feedstock containing appreciable quantities of organic nitrogen permits the hydrocracking reaction to be conducted at lower temperatures than is the case when such organic nitrogen content reduction is not accomplished. In cases where hydrocarbon feedstocks do not inherently have a desirably low organic nitrogen content, hydrofining of the feed is indicated, and may be accomplished in a conventional manner. For example, hydrofining may be accomplished at temperatures of 400 to 900 F., preferably 500 to 800 F., pressures of at least 300 p.s.i.g., and at liquid hourly space velocities of 0.3 to 5.0, in the presence of at least 500 s.c.f. of hydrogen per barrel of feed, and in the presence of a sulfur-resistant hydrogenation catalyst, for example a catalyst consisting of nickel sulfide, molybdenum sulfide and alumina.

HYDROCRACKING ZONE CATALYST .AND OPERATING CONDITIONS The catalyst in the first conversion zone, that is, the hydrocracking zone, in the process of the present invention may be a conventional acidic hydrocracking catalyst. The catalyst preferably contains a Group VIII hydrogenating component, preferably a sulfide. The catalyst also may contain a Group VI hydrogenating component, preferably a sulfide. The catalyst advantageously may comprise titania or zirconia, and tin or a compound thereof provides useful results, particularly when the catalyst also comprises nickel or a compound thereof. The cracking component of the catalyst may comprise any one or more of such acidic materials as silica-alumina, silicaalumina-titania, silica-alumina-zirconia, or crystalline zeolitic molecular sieves, preferably decationized type X or type Y faujasites. Particularly useful results are obtained with a catalyst comprising a crystalline zeolitic molecular sieve in particle form, and a matrix of other catalyst components in which the molecular sieve is dispersed. Said matrix advantageously may comprise a silica-containing gel, preferably silica-alumina, silica-alumina-titania, or silica-alumina-zirconia, and at least one Group VIII hydrogenating component, preferably nickel or a compound of nickel. Especially useful results are obtained if said matrix also contains a Group VI hydrogenating component, preferably tungsten or a compound of tungsten.

The operating conditions for the hydrocracking zone may be conventional hydrocracking conditions, for example a temperature in the range 400 to 800 F. and a pressure in the range 1500 to 3000 p.s.i.g., a liquid hourly space velocity of 0.1 to 5.0, preferably 0.3 to 3.0, a hydrogen rate of at least 2000 s.c.f. of hydrogen per barrel of hydrocarbon feed, preferably 3000 to 20,000 s.c.f. of hydrogen per barrel of hydrocarbon feed, and a per-pass conversion of 20 to 80 volume percent, preferably 40 to 60 volume percent, of the hydrocarbon feed to products boiling below the hydrocarbon feed boiling range.

The hydrocracking zone advantageously is operated with recycle thereto of at least a substantial portion of the liquid efiluent thereof that boils above the fraction passed from the hydrocracking zone to the second conversion zone.

SECOND CONVERSION ZONE CATALYST AND OPEMTING CONDITIONS The catalyst in the second conversion zone comprises at least one acidic cracking component and at least one hydrogenation-dehydrogenation component.

The acidic cracking component may be silica-alumina, silica-alumina-titania, silica-alumina-zirconia, halided alumina, a crystalline zeolitic molecular sieve, preferably a decationized type X or type Y faujasite, or other acidic component having utility in providing an acid cracking function for a hydrocarbon conversion catalyst.

The hydrogenation-dchydrogenation component may be a Group VIII metal or compound, for example nickel, cobalt, platinum or palladium or a compound of nickel, cobalt, platinum or palladium. Advantageously a Group VI metal or compound thereof will be present as an additional hydrogenation-dehydrogenation component, with molybdenum or tungsten, or a compound of molybdenum or tungsten, being preferred.

Any catalyst indicated herein to be a suitable catalyst for the first conversion zone also will be a suitable catalyst for the second conversion zone, including a catalyst comprising crystalline zeolitic molecular sieve particles and a silica gel-containing matrix in which said particles are dispersed.

The operating conditions for the second conversion zone are especially critical features of the process of the present invention. The operating temperature and pressure are selected within a temperature range of 825 to 950 -F. and a pressure range of 0 to 1500 p.s.i.g., preferably 0 to 1000 p.s.i.g., to accomplish the desired conversion with no net hydrogen consumption, and preferably with a net hydrogen production. The desired result is achieved with temperatures higher and pressures lower than are used in combination in modern conventional hydrocracking processes, which are operated with a net consumption of hydrogen.

The second conversion zone also is operated with a hydrogen-to-oil ratio of 3 to 15, preferably 5 to 12, and a cracking conversion of at least 15 weight percent, preferably at least 20 weight percent, and more preferably at least 30 weight percent, of the hydrocarbon feed to said second conversion zone to products boiling below the boiling range of said hydrocarbon feed.

The operating conditions in the second conversion zone may be adjusted within the above limits so that the zone operates in hydrogen balance, that is, with neither a net consumption nor a net production of hydrogen, within the spirit of the present invention. However, it is preferred that the operating conditions be adjusted within the above limits so that the zone operates with a net production of hydrogen, that is, with sufiicient dehydrogenation, particularly of naphthenic compounds, to produce more hydrogen than is required for operation of the zone, and particularly more than is required for the hydrocracking reactions proceeding therein concurrently with the naphthene dehydrogenation reactions.

DETAILED DESCRIPTION OF PROCESS SHOWN IN DRAWING Referring now to the drawing, there shown is an exemplary over-all process flow diagram suitable for carrying out the process of the present invention.

The hydrocarbon distillate feed is passed through line 1 into hydrocracking zone 2, and is contacted therein with a catalyst as previously described and with hydrogen supplied through line 3, at conditions previously described.

The effluent from hydrocracking zone 2 is passed through line 4 to gas-liquid separator 5, from which hydrogen is recycled to hydrocracking zone 2 through lines 6 and 3, and from which the liquid portion of said efiluent is passed through line 7 to fractionation zone 8.

The materials entering fractionation zone 8 through line 7 are fractionated in zone 8 into a gas fraction, which is withdrawn through line 9, a light hydrocracked naphtha product fraction, which is withdrawn through line 10, a fraction boiling generally above said light naphtha fraction, which is withdrawn through line 11, and a bottoms fraction, boiling generally above said fraction in line 11, which is withdrawn through line 12.

All or a portion of the fraction withdrawn through line 12 is recycled through line 13 to hydrocracking zone 2. When desired, a portion of the fraction in line 12 may be withdrawn from the system through line 14 for further processing elsewhere, or for other disposition.

The fraction in line 11 is passed therethrough to hydrocracking-dehydrogenation zone 15, and is contacted therein with a catalyst as previously described and with hydrogen supplied through line 16, at conditions previously described, adjusted to provide a net hydrogen production from zone 15.

The efiluent from hydrocracking-dehydrogenation zone 15 is passed through line 17 to gas-liquid separator 18, from which hydrogen is recycled to zone 15 through line 16, and from which the liquid portion of said effluent is passed through line 19 to fractionation zone 20.

The materials entering fractionation zone 20, upgraded compared with the hydrocarbon feed to zone 15, by hydrocracking and dehydrogenation of said feed in zone 15, are fractionated in zone 20 into a gas fraction, which is withdrawn through line 21, a light hydrocracked and dehydrogenated naphtha product fraction, which is withdrawn through line 22, a heavy hydrocracked and dehydrogenated naphtha product fraction, boiling generally above said light naphtha product fraction, which is withdrawn through line 23, a fraction, boiling generally above said heavy naphtha product fraction, which is recycled through line 24 and 11 to zone 15, and a bottoms fraction, boiling generally above said fraction in line 24, which is Withdrawn through line 25.

All or a portion of the fraction in line 25 may be recycled through lines 26, 24 and 11 to zone 15. When desired, a portion of the fraction in line 25 may be withdrawn from the system through line 27 for further processing elsewhere, or for other disposition.

Because more hydrogen is produced in zone 15 than is required to be recycled through line 16 to satisfy the requirements of the reactions in zone 15, the net production of hydrogen may be utilized by recycling it from line 16 through lines 28, 6 and 3 to zone 2 to aid m satisfying the hydrogen requirements of zone 2. Alternatively, all or a portion of said net production of hydrogen may be withdrawn from line 16 through line 29 for other uses.

CONCLUSIONS From the foregoing it may be seen that, compared with a conventional process comprising hydrocracking followed by reforming of the 180-400 F. heavy naphtha hydrocrackate, with recycle to the hydrocracking zone of all materials boiling above 400 F., the advantages of the process of the present invention include:

(1) Lesser amounts of heavy materials are recycled to the hydrocracking zone, freeing some of the capacity thereof for additional quantities of fresh feed.

(2) Instead of a reforming zone operating to upgrade only those hydrocracked materials boiling up to about 400 F., a hydrocracking-dehydrogenation zone is used that upgrades those materials and additional heavier materials that heretofore were recycled to the hydrocracking zone.

(3) The hydrocracking-dehydrogenation zone reduces the molecular 'weight of the 400 F materials supplied thereto, to produce 400 F. materials, and at the same time the octane number and other characteristics of the 400 F. portion of the hydrocrackate are also improved therein.

(4) No separate conventional reforming zone is necessary.

(5) The second conversion zone is operated with no net consumption of hydrogen, and may be operated with a net production of hydrogen; any net production of hydrogen may be used to help satisfy the hydrogen requirements of the first conversion zone.

All variations and modes of operation of the process of the present invention that are within the spirit of the invention are intended to be covered by the following claims.

What is claimed is:

1. A process for producing gasoline which comprises hydrocracking a petroleum distillate in a first conversion zone, separating the efiluent from said first conversion zone into a light naphtha fraction having an end boiling point between about 180 and 280 F., a second fraction having an initial boiling point between 180 and 280 F. and an end boiling point between about 500 to 600 F., and a third fraction boiling above about 500 F., hydrocracking and dehydrogenating said second fraction in a second conversion zone in the presence of a catalyst comprising an acidic cracking component and a hydrogenation-dehydrogenation component, at a hydrogen/oil ratio of 1 3 to 15, and at a combination of temperature and pressure that results in no net hydrogen consumption, said temperature being in the range 825 to 950 F., and said pressure being from 0 to 1500 p.s.i.g., and recovering from said second conversion zone at least one naphtha product.

2. A process as in claim 1, wherein said third fraction is recycled to said first conversion zone.

,3. A process as in claim 1, wherein a fraction boiling generally above said naphtha product is separated from the efiluent from said second conversion zone and is recycled to said second conversion zone.

4. A process as in claim 1, wherein said second conversion zone is operated with a net production of hydrogen.

5. A process as in claim 4, wherein hydrogen is recycled from said second conversion zone to said second conversion zone and to said first conversion zone.

References Cited UNITED STATES PATENTS 3,047,490 7/1962 Myers 20859 3,216,923 11/1965 Haensel 208---139 3,132,087 5/1964 Kelley et al 208-- 3,506,566 4/1970 Haney 20860 DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner US. Cl. X.R. 20860, 141 

